Since the early 1980s several research projects and demonstration programs have attempted to employ natural gas as a fuel for locomotives. The initial motivation was to determine if any reduction in emission levels could be obtained compared to diesel locomotives, while maintaining the same level of power. These efforts were driven by evolving emission standards for locomotives from the Environment Protection Agency (EPA), for which in 1997 the EPA established Tier 0, 1 and 2 standards, and more recently in 2008 they set the Tier 3 and 4 standards. Both the Tier 3 and 4 standards dramatically reduce emissions of diesel particulate matter (PM) and nitrogen oxide (NOx). Out of these efforts only one commercially available, proven and tested natural gas fuelled line-haul locomotive emerged, which employed a low pressure injection technology. In a paper titled “An Evaluation of Natural Gas-fueled Locomotives”, published in November 2007 by BNSF Railway Company, Union Pacific Railroad Company (UPRR), the Association of American Railroads, (together known as the Railroads) and the California Environmental Associates, the Railroads position on natural gas fuelled locomotives was presented. Except for some potential niche applications, the Railroads did not believe there is an opportunity to use natural gas as a locomotive fuel to help meet emissions and performance goals. This position was based on the one known commercially available natural gas fuelled line-haul locomotive available in North America. This product was a conversion kit for the EMD 645 two-stroke diesel engine that enables the locomotive to run on liquefied natural gas (LNG) as a primary fuel, while employing diesel as a pilot fuel. The LNG fuel is vaporized and injected at low pressure (85-125 pounds per square inch (psi)) such that the fuel and air mix during compression. A small portion of diesel “pilot” fuel is then injected into the cylinder at the top of the stroke where it auto-ignites to facilitate combustion.
Several of the research projects and demonstration programs attempted high pressure injection techniques where natural gas fuel was injected late in the compression cycle. In 1992 the UPRR began two of these efforts in separate programs with Electro Motive Diesel (EMD) and GE Transportation Systems (GE) to investigate the use of natural gas in line-haul, high-horsepower locomotive engines. This was a significant, multi-year effort in which UPRR expended over $15 million exploring basic engine and fueling technology issues. The natural gas injection pressures employed in both the EMD and GE systems were in the range between 3000 psi and 4500 psi. Due to technical limitations, the locomotives developed separately by EMD and GE were incapable of revenue operation. The technical difficulties in both programs included failure of gas injectors, cryogenic LNG pumps for handling the cryogenic fuel between the tender tanks and the locomotives, the engine control system software, the gas transition control system software, and fuel system joint leaks.
The conversion kit for the EMD 645 developed out of a project started by Burlington Northern Railroad (BN) in 1987 involving a two pronged effort to develop natural gas fueling infrastructure and line-haul locomotives capable of running on natural gas. For the fueling infrastructure, BN worked with Air Products and Chemicals (APC) to develop fueling locations and cryogenic tank equipped tender cars to support the use of Refrigerated Liquid Methane (RLM), a high purity form of liquefied natural gas, as a locomotive fuel. In a paper titled “LNG as a Fuel for Railroads: Assessment of Technology Status and Economics”, published by the Gas Research Institute in January 1993, Bob Kirkland of APC indicates that LNG vaporization can be performed on the locomotive or on the tender car. “As less energy is needed to pump a liquid than to compress a gas, future tender car designs will likely deliver liquid to a pump located on the locomotive and upstream of the vaporizer. It would be impractical, according to Bob Kirkland of Air Products, for the tender car to supply high pressure liquid to the locomotive. Such an arrangement would involve long lengths of high-pressure piping as well as additional hardware between the locomotive and the tender car to power the pump.”
Based on the admissions of the Railroads and the results of the research and demonstration projects cited above, it is evident that late cycle, high pressure direct injection of natural gas in a locomotive engine is not a straightforward or obvious undertaking. Several technical challenges exist that have prevented a commercially available natural gas locomotive line-haul product from emerging that can challenge and improve upon the emissions from so called clean diesel locomotive technologies.
The present method and apparatus provide an improved technique for supplying a gaseous fuel from a store of the gaseous fuel on a tender car to an internal combustion engine of a locomotive for combustion.